Optomechanical cycles of photochromic-polymer microsystems induced by laser irradiation

Abstract

Molecular microsystems, which can operate as actuators, are of high current interest in a variety of diverse micromechanical applications. We present novel polymer-based microsystems, which undergo optomechanical cycles induced by ns laser pulses. It is demonstrated that these opto-actuators can be accurately controlled in a step-by-step manner by proper manipulation of the incident laser pulses. The photoinduced actuation relies on the reversible photochemical changes of photochromic spiropyran molecules incorporated into polymer matrices. In particular, the spiropyran molecule is converted reversibly between its isomeric forms, upon irradiation at appropriate laser wavelengths. These photochromic inter-conversions were found to activate the polymer matrix, resulting in its contraction and lengthening in a highly controllable manner. The reversible optomechancial actuation is demonstrated by laser-induced bending of microcantilevers made of photochromic polymers. The pathways of the optomechanical cycles are being well defined and correlated with stereoisomeric states of the photochromic dopants. The correlation is performed after fluorescence emission measurements of the photochromes in polymers matrices, upon appropriate pulsed laser irradiation.